I remember being fascinated with this concept some years ago and reading some articles about others experiences with same. I do not recall reading of any structural failures, but I can't remember the type of models that were being covered. I assumed that they were using shopping bag brown paper. Try finding that today.
The heat induced polymerization of the aliphatic glue was what added the real strength, IIRC.
AFAIK shopping bag paper is the right stuff to use -- I suspect that you could find butcher paper ('kraft paper') to match.
I ran across a web site ages ago on vacuum bagging wings that mentioned using epoxy/paper instead of epoxy/carbon.
I wouldn't discount the strength of the paper -- if you leave those wood fibers relatively unmolested (like, don't bleach the heck out of them) you have a material that's pretty strong as long as it doesn't buckle -- and gluing it to foam should be a pretty good way to keep it from buckling.
Come to think of it, I wonder if you could use paper-reinforced balsa on the front ends of fuselages, instead of ply doublers. Hmm. Probably would be too rigid & not tough enough.
I think it was (or perhaps still is) popular with CL combat flyers who needed to mass-produce lots of good airframes on the cheap. Now they just buy them by the dozen from the Czech republic.
That is what I remember seeing used. You can see the fibers in it and they are long and overlapping. Sealing it with something would make them stay where they are and that is what provides the strength, but that is only in compression and sheer...which is where we need the strength fortunately.
I think it would be too rigid. I use thin ply and good contact cement because I want a little flexing and bending in such places.
The problem, as I remember, is that the paper has to absorb the epoxy, whatever, and it can absorb a lot...consequently, it is a heavy way to finish. If you had a thinned aliphatic resin and cut strips of the paper and put it on the surface at criss-crossing 45 degrees (after getting the paper soaked with thinned glue, that might end up being very strong, take compound curves, and be easier to apply. Once it was dry, it should be pretty tough. I use such resin in unusual places. Normally, the outside would dry and seal the inside which might never dry...unless the piece was put in the microwave oven to "boil out" the water. It is good to put a cup of water in the oven at the same time to serve as a "load" so as to not the klystron unhappy.
Simply soak the paper in water, use builders grade thinned PVA and slap the wet paper on. I used ordinary parcel wrapping paper with a shiny and a dull side. Makes little difference which side you use..
Afterwards I sprayed with cellulose..that was a big problem when I sanded through the paper :D
Its heavier than epoxy glass...or WBPU glass, and not as strong, but it sure is cheap!
And pretty string too. And takes paint really well.
One of the first links listed at Alan's Hobby, Model & RC Web Links
= refer to Covering Foam Wings With Ordinary Brown Paper = Article Stats Rating: 4.06 Votes: 139 Hits: 12385 By Steve Kerrey July
01, 1996 under Covering Materials & Instructions (see also Colours & Visibility above)
Chemical Compatibility of Common Model Finishing Materials Cover Foam Wings With Brown Paper - Ezone ************************ Covering - Lee Van Tassle Cover small models with tissue - M.A.N. tips. Covering & Painting Techniques*** Covering tips & techniques - RCU article Coverite Home Page Fibreglass Cloth Covering by Jim Ryan Klass Kote (epoxy paint) Lite Films,Covering & colouring & weights - Roy Bourke Light plastic film - types & techniques for micro flyers - M.A.N article Monokote - How to. MonoKote & LustreKote Surface Preparation & Painting Oracover = Ultracote = Profilm . Hobby Lobby's tips Oracover - Holland Ozcover Painting Canopies (Heli) - email Alan for file. Painting RC models with Latex Paint Pennyplane - lightweight building & covering for indoor duration Poly-Fiber Polyester Fabrics Polyurethane (Water based) - adhere and finish fibreglass and Koverall cloth etc. RhinoCover Base White Scale Rib Stitch Silk (Thai silks) Silkspan Covering - How to and Why Solite - How to apply this ultra lite film Solite - Advanced Covering Techniques SPAD (Simple Plastic Model Design) - use of plastics Tinting Clear Canopies - David Tatosian. (site down - email Alan direct for copy.) Two Color Covering - RCFU Ultracote® ( = ProFilm =OraCover) Tips & Tricks = Horizon Hobby : USI Laminate: Use 3mm thick film
regards Alan T. Alan's Hobby, Model & RC Web Links
Been there, done that a few times now. Got the basic instructions from a magazine article some time ago.
Cut your brown paper to size, ie. one side of a foamie, one side of a fuselage or whatever you are going to cover. Best to cut it a bit oversize and trim after it has dried.
Go soak that piece of brown paper in the sink/bath in warm water. When it is thoroughly soaked hang it over the shower rail, or whatever to drain.
While the paper is draining coat the area of wing/fuselage you are about to cover with dilute PVA... I use it neat instead of diluted.
Go get your piece of brown paper and apply it to the part you have just covered in glue... you can peel it off and re-apply to get it lined up. Smooth it down with a brush and/or credit card to get rid of any air bubbles. Soaking the paper makes it easier to work into place and also allows the PVA glue to penetrate right into the paper.
Now coat the brown paper with a further layer of diluted (again I use neat) PVA.
Go have a beer and leave it to thoroughly dry out.
It's quite similar to covering a model with heat shrink film, except I wouldn't advocate it's use over open wing bays.
When it's all coated and dry I sand it smooth and then apply a couple of coats of acrylic varnish.
Choose the weight of brown paper you want from what is available and how much strength you wish to get in the finished wing/fuselage.
The glue and the acrylic varnish are both water based and don't add much weight when they have dried. The brown paper is dark coloured and can take a bit of colouring to prevent it showing through.
Cover with paint or heat shrink film as per normal.
The finished result is very strong and gives a good degree of `ding' proofing to soft balsa. One you try it you will be impressed with the strength and hardness of the coated wing/fuselage.
That's brown paper covering....
I also use greaseproof paper for some jobs. It is very strong because of the way the pulp is `worked' to produce it. It is white so is easier to cover. Soaking it thoroughly seems to work as well as with the brown paper method. It is harder to apply and needs more care as it traps air bubbles more readily...... try it on some test pieces first. I use greaseproof to cover the sheeted area of D box wings, being thin it doesn't make a lot of difference to the profile, but it does give a lot of strength to the thin balsa sheeting.
I fly gliders off slope and also thermal soaring so I don't set out to make a lead sled, but I regularly use brown paper or greaseproof to give strength, stiffness and a harder surface finish.
If used both outside and inside the fuselage I reckon you could do away with the heavier ply doublers... I have yet to try this...
Yes, I did. I don't know why I wrote "klystron". If you think that is bad, you should see the postings I got on a music group when I said that Buddy Hackett played tenor guitar in his own group a long time before become a studio cornet player. I meant "Bobby"...not "Buddy," the comedian. Then I forgot 1933 for 1939 and had him playing cornet before guitar. This is happening more and more often...I don't know why I do... I do... well...I forgot now what it is that I do but I know I don't know why I do it. That does remind me of an old song for children that now applies to we now...less-young...folk.
I have been doing paper covered foam wings for CL combat for years. Anymore only the leading edge back to the high point is covered with paper to save weight on the "disposable" combat models being built. The paper is white "banner paper" from an office supply store (comes in different weights so look for the thinner paper as it can get quite heavy). You can usually get 24" wide rolls that are about 100 feet long. I cut the paper to size (maybe an inch more all the way around that I trim off later). Spray it with water to keep it from absorbing too much glue and use thinned white glue (to a brushing consistancy) to put the paper on. I overlap only at the middle of the wing maybe 6". Be careful to do both sides at once as the paper shrinks alot as it dries and can warp a wing (kinda like covering with tissue and dope). Get as many wrinkles out as you can while it is wet. It will feel like it is far too heavy till the glue dries... then you have little more than the weight of the paper. Finish with an low temp iron on film to fuel proof things. If anything this technique makes the wing too strong as I break 1/2" by
3/4 maple motor mounts glued to a pine center rib when I crash a combat plane with this construction. Also you CANNOT get a warp out and will need to use a trim tab if you build one in.
Same here, I fly RC-combat, and coat both fuse and wing with brown kraft paper 70 grams/m^2. over foam. Wet well, and apply with water based floor acrylic. This does shrink very little, and when dry is very tough and light. It also is fuel resistant and repairs well. The wing has no spar, just a core of a light roofmate variety, and a hard balsa foil nose . The centre section is reinforced with two extra paper layers. The aileron hinge line on top of the foil is reinforced with one extra layer of paper. (no hinges, just paper). The aileron is cut loose from the bottom upward, and no extra further work is done. Model half-time is too short for that.